# I Firing a pistol in an environment with no external forces

1. Sep 28, 2016

### orthogonal1

If one fires a pistol while holding it in one's hand, the pistol will exert a backwards force above the grip of the hand, causing the gun to both move backwards as well as exerting a torque, as the hand is essentially behaving as a fulcrum. If a pistol is fired in a gravity-free environment with no air resistance, and the pistol fires, and the backwards force occurs above the gun's centre of mass, will a torque be exerted and will the gun thus be made to rotate as well as move backwards?

This question is puzzling because nothing acts as a fulcrum aside from perhaps it's centre of mass(?)

2. Sep 28, 2016

### jbriggs444

A fulcrum is not required for rotation. A torque contributes to angular momentum regardless.

How about analyzing the problem with a free body diagram. One drawing to represent the pistol, the impulse from firing and the impulse from the hand. A second drawing to represent the pistol, the impulse from firing and no impulse from the hand.

3. Sep 28, 2016

### A.T.

You are aware that spacecraft use reaction engines to change orientation for decades now?